0-1 Knapsack Problem : Given two n-tuples of positive numbers (<V1,V2,.....,Vn) and (<w1,w2,w3,.....,wn and W>0, We wish to determine the subset T∈{1,2,3,....,n} (of files to store)) that maximizes ∑ieT Vi subject to ∑ieT wi≤W

Implicit Constraints : The implicit constraints are rules that determine which of the tuples in the solution space of I satisfy the criterion function.Thus implicit constraints describe the way in which the xi must relate to each other.

The Formulation of the backtracking : T(X1,X2,...,Xi): set of all possible values for xi+1 such that (X1,X2,...,Xi,Xi+1) is also a
Bi+1>(X1,X2,...,Xi,Xi+1): bounding function
If Bi+1>(X1,X2,...,Xi,Xi+1) is false, then the path cannot be extended to reach an answer node.